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Positron beams and two-photon exchange: The key to precision form factors

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Abstract

The proton elastic form factor ratio can be measured either via Rosenbluth separation in an unpolarized beam and target experiment, or via the use of polarization degrees of freedom. However, data produced by these two approaches show a discrepancy, increasing with Q2. The proposed explanation of this discrepancy - two-photon exchange - has been tested recently by three experiments. The results support the existence of a small two-photon exchange effect but cannot establish that theoretical treatment at the measured momentum transfers are valid. At larger momentum transfers, theory remains untested. This paper investigates the possibilities of measurements at DESY and Jefferson Lab to measure the effect at larger momentum transfers.

Original languageEnglish
Title of host publicationInternational Workshop on Physics with Positron at Jefferson Lab
EditorsEric Voutier, Joseph Grames
PublisherAmerican Institute of Physics Inc.
ISBN (Electronic)9780735416772
DOIs
StatePublished - May 25 2018
EventInternational Workshop on Positron Physics at Jefferson Lab, JPos 2017 - Newport News, United States
Duration: Sep 12 2017Sep 15 2017

Publication series

NameAIP Conference Proceedings
Volume1970
ISSN (Print)0094-243X
ISSN (Electronic)1551-7616

Conference

ConferenceInternational Workshop on Positron Physics at Jefferson Lab, JPos 2017
Country/TerritoryUnited States
CityNewport News
Period09/12/1709/15/17

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